Here are the key points I extracted.
1. WLC management interface MUST have a vlan tag in order to have proper wireless QoS ( In other words WLC management IP should not be on the same vlan where you configure as native vlan on the WLC-SW trunks. Native vlan & WLC Management vlan shoud be on two different vlans.)
2. If you deploying voice, video, data services through single WLAN, “WMM- Required” is the option you have to select. (If you select “WMM-Allowed” and if that WLAN is configured for platinum QoS then all non-WMM traffic will tagged with voice priority)
3. WLC only can do CoS based tagging, so you have to trust CoS (ie “mls qos trust cos”) on the switch ports connected to WLC.